Add generic session UUID structures to DNA

Allows to use pre-defined structure for session UUIDs in all data
structures which needs it: pose channels, sequencer strips, modifiers.

The goal of all this is to have a reliable way of matching original
and copy-on-written versions of data, so that it's possible to
preserve runtime caches.

1 files changed, 46 insertions, 0 deletions

diff --git a/source/blender/makesdna/DNA_session_uuid_types.h b/source/blender/makesdna/DNA_session_uuid_types.h
new file mode 100644
index 00000000000..d2ec0eb3de1
--- /dev/null
+++ b/source/blender/makesdna/DNA_session_uuid_types.h
@@ -0,0 +1,46 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup DNA
+ */
+
+#ifndef __DNA_SESSION_UUID_TYPES_H__
+#define __DNA_SESSION_UUID_TYPES_H__
+
+#include "BLI_sys_types.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Is a structure because of the following considerations:
+ *
+ * - It is not possible to use custom types in DNA members: makesdna does not recognize them.
+ * - It allows to add more bits, more than standard fixed-size types can store. For example, if
+ *   we ever need to go 128 bits, it is as simple as adding extra 64bit field.
+ */
+typedef struct SessionUUID {
+  /* Never access directly, as it might cause a headache when more bits are needed: if the field
+   * is used directly it will not be easy to find all places where partial access is used. */
+  uint64_t uuid_;
+} SessionUUID;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __DNA_SESSION_UUID_TYPES_H__ */